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MIPS pseudo instructions
In MIPS, some operations can be performed with help of other instructions. The most common operations are unified in pseudo-instructions — they can be coded in assembly language, and assembler will expand them to real instructions according to following rules:
Name | Assembly syntax | Expansion | Operation in C |
---|---|---|---|
Data moves | |||
move | move $t, $s |
addiu $t, $s, 0 |
t = s |
clear | clear $t |
addu $t, $zero, $zero |
t = 0 |
load 32-bit immediate | li $t, C |
lui $t, C_hi ori $t, $t, C_lo
|
t = C |
load address | la $t, C |
lui $at, 0x1001 ori $t, $at, C
|
t = 0x10010000 I C |
Branches | |||
branch unconditionally | b C |
beq $zero, $zero, C |
goto PC + 4 + (C << 2) |
branch unconditionally and link | bal C |
bgezal $zero, C |
ra = PC + 8; goto PC + 4 + (C << 2) |
branch if greater than | bgt $s, $t, C |
slt $at, $t, $s bne $at, $zero, C
|
if (s > t) goto PC + 4 + (C << 2) |
branch if less than | blt $s, $t, C |
slt $at, $s, $t bne $at, $zero, C
|
if (s < t) goto PC + 4 + (C << 2) |
branch if greater than or equal | bge $s, $t, C |
slt $at, $s, $t beq $at, $zero, C
|
if (s >= t) goto PC + 4 + (C << 2) |
branch if less than or equal | ble $s, $t, C |
slt $at, $t, $s beq $at, $zero, C
|
if (s <= t) goto PC + 4 + (C << 2) |
branch if greater than unsigned | bgtu $s, $t, C |
sltu $at, $t, $s bne $at, $zero, C
|
if (s > t) goto PC + 4 + (C << 2) |
branch if zero | beqz $s, C |
beq $s, $zero, C |
if (s == 0) goto PC + 4 + (C << 2) |
Multiplications/Divisions | |||
multiplicate and return 32 bits | mul $d, $s, $t |
mult $s, $t mflo $d
|
d = (s * t) & 0xFFFFFFFF |
quotient | div $d, $s, $t |
div $s, $t mflo $d
|
d = s / t |
remainder | rem $d, $s, $t |
div $s, $t mfhi $d
|
d = s % t |
Jumps | |||
jump register and link to ra | jalr $s |
jalr $s, $ra |
ra = PC + 4; goto s; |
Logical operations | |||
not | not $t, $s |
nor $t, $s, $zero |
t = ~s |
No-operations | |||
nop | nop |
sll $zero, $zero, 0 |
{} |
In fact, every MIPS instruction that has $zero
as its destination and doesn't access memory and/or I/O system, can be treated as a nop
; but using sll $zero, $zero, 0
is the most convinient because it's byte code is all-zeroes 0x00000000
.
Since 2014/2015, you don't have to implement pseudo-instructions output in MIPT-MIPS assignments, all instructions must be printed as real MIPS instructions. Unexpanded pseudo-instructions are left only in testing traces source files (.s
files).
MIPT-V / MIPT-MIPS — Cycle-accurate pre-silicon simulation.